It is known to coat an article such as, for example, a mug, kettle or dish with thermochromatic ink such that when the article undergoes a temperature change by, for example, hot liquid being poured thereinto, an image disposed on the article becomes visible as the thermochromatic ink becomes transparent, and when the article cools, the image "disappears." Also known are thermochromatic inks that change from opaque to transparent as its temperature changes from hot to cold. With such inks, images can be made to "disappear" when the article is heated.
U.S. Pat. No. 5,223,958 to Berry describes a well-known article that incorporates thermochromatic ink in an amusement device that is heat activated. Berry's amusement device comprises a supporting substrate, a layer of micro encapsulated thermochromatic liquid crystal material disposed on the substrate and an outer transparent film having a message or visual image thereon. The requirement of a separate layer to carry the image, however, contributes to increased manufacturing costs in terms of both materials and process steps. Moreover, the Berry reference fails to provide any sort of protection for the transparent film. That is, the transparent film easily can be damaged by scratching or the like. Moreover still, an article manufactured in accordance with the disclosure of Berry is deficient in that no protection is afforded when the article is subjected to relatively harsh conditions, such as those presented by an automatic dishwasher.
U.S. Pat. No. 5,219,625 to Matsunami et al. is similar to Berry and discloses a thermochromatic laminate member having a base layer, a thermochromatic layer, and a thin transparent iridescent film laminated on the thermochromatic layer. Color patterns on the film become visible once the thermochromatic layer becomes clear after heating. An article fabricated in accordance with Matsunami et al., however, like an article made in accordance with Berry, requires a separate transparent film over the thermochromatic ink and, further, is susceptible to harsh conditions, wherein the laminate and even the thermochromatic ink layer can be damaged.